A problem that arises in known filling systems is that sometimes, under certain conditions, in particular including under operating conditions, gas and/or vapor that does not belong to the charge enters the interior of the filling element or the liquid channel thereof. Examples of foreign gases that may inadvertently enter include, for example, air and/or residues of a cleaning and/or disinfecting medium in gas and/or vapor form that was used to clean and/or disinfect the filling system or filling machine.
There are certain times when the filling machine is particularly vulnerable to entry of gaseous contaminants. These include after cleaning the filling machine and before filling starts again, for example after a change of product. Filling machines are also vulnerable to entry of gaseous contaminants during unfavorable flow conditions at the mouth or dispensing opening of the filling element. These conditions can exist at the start of the filling process for a particular container. Sometimes, gaseous contaminants enter during start-up of a filling machine, or after a break in production.
Gas entering the filling machine causes many problems.
One problem is that gas bubbles may rise inside the product lines or channels. These bubbles can reach the charge-providing vessel in a filling machine. Germs carried by gas in the bubbles may contaminate the charge. Since the charge-providing vessel is common to all filling elements, this would impact not only the particular filling element but all filling elements.
Another problem is that gas bubbles impair the measurement accuracy of flow-measuring equipment. This, in turn, impairs the ability to control the filling volume of the containers. As a result, containers may have too much or too little charge in them.
One way to avoid difficulties caused by gas in the filling system is to pass a relatively large quantity of charge through the filling elements of a filling machine in a pre-running mode prior to the actual start of production, and then to discard this charge. This is wasteful. Additionally, no containers are fed to the filling machine during this pre-running mode. This means that copious quantities of charge flow freely onto the floor. This results in a mess with that must be cleaned up.